Hybrid Laminar Flow Control Applied to Advanced Turbofan Engine Nacelles 920962

In recent years, the National Aeronautics and Space Administration (NASA) in cooperation with U.S. industry has performed flight and wind-tunnel investigations aimed at demonstrating the feasibility of obtaining significant amounts of laminar boundary-layer flow at moderate Reynolds numbers on the swept-back wings of commercial transport aircraft. Significant local drag reductions have been recorded with the use of a hybrid laminar flow control (HLFC) concept. In this paper, we address the potential application of HLFC to the external surface of an advanced, high bypass ratio turbofan engine nacelle with a wetted area which approaches 15 percent of the wing total wetted area of future commercial transports. A pressure distribution compatible with HLFC is specified and the corresponding nacelle geometry is computed utilizing a predictor/corrector design method. Linear stability calculations are conducted to provide predictions of the extent of the laminar boundary layer. Performance studies on an advanced twin-engine transport configuration are presented to determine potential benefits in terms of reduced fuel consumption.